Young Horses Require Special Deworming Considerations

Because foals are more susceptible to parasite infection and have an elevated risk for developing disease, properly scheduled deworming treatments are extremely important.

Photo: Anne M. Eberhardt/The Horse

As the breeder and owner of a new foal, you are looking to the future. You imagine that foal growing and running in the field at the mare’s side. You look forward the countless hours of training and preparation ahead. You imagine competing and, even more, winning.

But can you imagine sickness or even death from something like parasites? Prior to the development of effective dewormers, horses of all ages often suffered and died from parasite infections. And some deworming practices have resulted in a rise of parasite resistance and reduced efficacy in certain drug classes.

“It is critical that we take parasite resistance seriously and become better managers of our horses,” said Nathan Voris, DVM, equine technical services veterinarian for Zoetis. “If we don’t take the time to evaluate our deworming practices, then we will likely see health problems that haven’t occurred since our grandfathers’ time.”

Research has shown internal parasites are becoming resistant to current anthelmintics (dewormers). Taking steps to fight resistance and improve parasite management will help maintain peak performance in our horses, Voris explained.

“Because anthelmintic resistance is an inherited trait in parasites, horse owners must adjust their traditional deworming practices,” Voris said. “Otherwise, the currently available dewormers will become less effective. Greater parasite burdens will likely lead to serious health problems in the future with fewer effective options to combat parasites.”

The American Association of Equine Practitioners (AAEP) has recently published new parasite control guidelines. Rather than treating a group of horses exactly the same way, the new guidelines suggest treating animals as individuals.

The guidelines specify that horses less than 3 years old require specialized attention when it comes to parasite control. Because they are more susceptible to parasite infection and have an elevated risk for developing disease, properly scheduled deworming treatments during this phase are extremely important.

“The most problematic parasites in foals and young horses are roundworms, which are also called ascarids,” Voris said. “Left untreated, ascarids are a serious health threat that can cause severe, lasting health problems.”

The AAEP parasite control guidelines suggest ways to keep parasites in check and keep foals healthy and growing. Not following the recommended guidelines can put your foal at risk for stunted growth, colic, or many other health problems.

A few points Zoetis suggests remembering about deworming foals and young horses:

Foals should be dewormed at least four times in the first 12 months of life.

A fecal egg count (FEC) is recommended at weaning to determine whether worm burdens are primarily strongyles or ascarids to help choose the correct treatment option.